Fix collections.abc.Seqs on 3.9+, where they should be used

HISTORY.rst

@@ -4,7 +4,9 @@ History
 
 1.4.0 (UNRELEASED)
 ------------------
-* Fix an issue with `GenConverter` un/structuring hooks when a function hook is registered after the converter has already been used.
+* Fix an issue with ``GenConverter`` un/structuring hooks when a function hook is registered after the converter has already been used.
+* Add support for ``collections.abc.{Sequence, MutableSequence, Set, MutableSet}``. These should be used on 3.9+ instead of their ``typing`` alternatives, which are deprecated.
+  (`#128 <https://github.com/Tinche/cattrs/issues/128>`_)
 
 1.3.0 (2021-02-25)
 ------------------

src/cattr/_compat.py

@@ -97,6 +97,12 @@ def is_bare(type):
         _SpecialGenericAlias,
         _UnionGenericAlias,
     )
+    from collections.abc import (
+        MutableSequence as AbcMutableSequence,
+        Sequence as AbcSequence,
+        MutableSet as AbcMutableSet,
+        Set as AbcSet,
+    )
 
     def is_tuple(type):
         return (
@@ -117,12 +123,26 @@ def is_union_type(obj):
 
     def is_sequence(type: Any) -> bool:
         return (
-            type in (List, list, Sequence, MutableSequence, tuple)
+            type
+            in (
+                List,
+                list,
+                Sequence,
+                MutableSequence,
+                AbcMutableSequence,
+                tuple,
+            )
             or (
                 type.__class__ is _GenericAlias
-                and issubclass(type.__origin__, Sequence)
+                and issubclass(
+                    type.__origin__,
+                    Sequence,
+                )
+            )
+            or (
+                getattr(type, "__origin__", None)
+                in (list, tuple, AbcMutableSequence, AbcSequence)
             )
-            or (getattr(type, "__origin__", None) in (list, tuple))
         )
 
     def is_mutable_set(type):
@@ -132,7 +152,10 @@ def is_mutable_set(type):
                 type.__class__ is _GenericAlias
                 and issubclass(type.__origin__, MutableSet)
             )
-            or (getattr(type, "__origin__", None) is set)
+            or (
+                getattr(type, "__origin__", None)
+                in (set, AbcMutableSet, AbcSet)
+            )
         )
 
     def is_frozenset(type):

tests/metadata/__init__.py

@@ -1,7 +1,23 @@
 """Tests for metadata functionality."""
 import sys
 from collections import OrderedDict
-from typing import Any, Callable, Dict, List, Tuple, Type, TypeVar
+from collections.abc import (
+    MutableSequence as AbcMutableSequence,
+    Sequence as AbcSequence,
+    Set as AbcSet,
+    MutableSet as AbcMutableSet,
+)
+from typing import (
+    Any,
+    Callable,
+    Dict,
+    List,
+    MutableSequence,
+    Sequence,
+    Tuple,
+    Type,
+    TypeVar,
+)
 
 import attr
 from attr import NOTHING
@@ -65,6 +81,8 @@ def simple_typed_attrs(
             | str_typed_attrs(defaults)
             | float_typed_attrs(defaults)
             | dict_typed_attrs(defaults)
+            | mutable_seq_typed_attrs(defaults)
+            | seq_typed_attrs(defaults)
         )
     else:
         return (
@@ -78,6 +96,8 @@ def simple_typed_attrs(
             | list_typed_attrs(defaults)
             | frozenset_typed_attrs(defaults)
             | homo_tuple_typed_attrs(defaults)
+            | mutable_seq_typed_attrs(defaults)
+            | seq_typed_attrs(defaults)
         )
 
 
@@ -212,7 +232,15 @@ def set_typed_attrs(draw, defaults=None):
     val_strat = sets(integers())
     if defaults is True or (defaults is None and draw(booleans())):
         default = draw(val_strat)
-    return (attr.ib(type=set[int], default=default), val_strat)
+    return (
+        attr.ib(
+            type=set[int]
+            if draw(booleans())
+            else (AbcSet[int] if draw(booleans()) else AbcMutableSet[int]),
+            default=default,
+        ),
+        val_strat,
+    )
 
 
 @composite
@@ -253,6 +281,48 @@ def list_typed_attrs(draw, defaults=None):
     )
 
 
+@composite
+def mutable_seq_typed_attrs(draw, defaults=None):
+    """
+    Generate a tuple of an attribute and a strategy that yields lists
+    for that attribute. The lists contain floats.
+    """
+    default = attr.NOTHING
+    val_strat = lists(integers())
+    if defaults is True or (defaults is None and draw(booleans())):
+        default = draw(val_strat)
+    return (
+        attr.ib(
+            type=Sequence[int]
+            if not is_39_or_later or draw(booleans())
+            else AbcSequence[int],
+            default=default,
+        ),
+        val_strat,
+    )
+
+
+@composite
+def seq_typed_attrs(draw, defaults=None):
+    """
+    Generate a tuple of an attribute and a strategy that yields lists
+    for that attribute. The lists contain floats.
+    """
+    default = attr.NOTHING
+    val_strat = lists(floats(allow_infinity=False, allow_nan=False))
+    if defaults is True or (defaults is None and draw(booleans())):
+        default = draw(val_strat)
+    return (
+        attr.ib(
+            type=MutableSequence[float]
+            if not is_39_or_later
+            else AbcMutableSequence[float],
+            default=default,
+        ),
+        val_strat,
+    )
+
+
 @composite
 def homo_tuple_typed_attrs(draw, defaults=None):
     """